Yes, DC-DC conversion is used in many things, good example is a camera flash - the flash discharge tube needs a few hundred voltsand the usual technique is a power oscillator driving a step-up transformer, and the transformer secondary is rectified to chargea capacitor. Have a google around for camera flash driver circuits - there will be lots of examples I suspect.

For lower voltages DC-DC conversion often uses a boost or buck or boost-buck switch-mode circuit - avoiding needing a transformer,but requiring a inductor.

And any convenient switching device can be used for driving these circuits, either bipolar or MOSFET. (In the very olddays the oscillator might be electromechanical even!).

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